Process of desulfurizing ores.



UNITED STATES PATENT OFFICE- HOWARD I. WIEBUM, OF UPPER MONTCLAIR, NEW JERSEY, ASSIG-NOR TO THE SULPHUR SYNDICATE LIMITED, 01' LONDON, ENGLAND, A CORPORATION.

PROCESSOF DESULFURIZING OBES.

No Drawing.

To all whom it may concern:

Be it known that I, HOWARD F. WIERUM',-

, tain new and useful Improvements in Processes of Desulfurizing Ores, of which the following is a specification.

This invention relates to a method of operating desulfurizing furnaces, in which such an ore as pyrites, pyrrhotite, or other sulfid ores or mattes, or mixtures thereof 'are' roasted to remove the bulk of the sulfur of said ores or m attes, and to convert the major portion of the metals containedtherein into oxids, in such a manner as to prevent the escape of any considerable quantities of oxids of sulfur into the atmosphere, in such a manner as to recover if. possible, all or the major part of the sulfur eliminated from the ore, in the form of elemental sulfur.

In carrying out my process any type of roaster, similar to the McDougall, Wedge or Herreshoff or practically any conventional type, may be employed.

In carrying out my invention, I preferably proceed as follows :-Theore is fed, preferably in a continuous manner into the compartment, preferably the uppermost compartment of the furnace in the case of a .multiple hearth furnace, and in said compartment I maintain a non-oxiding atmoshere, for example by the admission of flames of oil or gas, which flames are nonoxidizing, and are not highly reducing. It is preferable to maintain these flames as nearly neutral as possible, but since it is impossible to continuously maintain the flames absolutely neutral, it is advisable to have the flames very slightly reducing. In this zone ofthe furnace, which may comprise one or more hearths, the ore is subjected to a temperature at which the major portion of the feeble atom of sulfur is distilled off. Without limiting myself to any particular temperatures, I will state that with ordinary pyrites ore containing copper, a temperature of 750 C. to 900 C. may be employed in this zone. During the passage of the ore through this zone .the bulk of the feeble atom of sulfur in the pyrites is driven off.

Specification of Letters Patent.

Patented May 16, 1916.

Application filed December 29, 1914. Serial No. 879,614.

The ore from which the major portion of v the less feeble atom has'thus been distilled may be then caused to travel to and through another section or zone of the furnace, in which a highly reducing atmosphere: is maintained, and a temperature as high as possible is maintained, without melting or fritting the ore passing through it. In this section of the furnace little orno chemical or physical action is performed on the ore, the. function of this section "of the furnace, in which the highly reducing hot atmosphere is maintained, by means of strongly reduc-- ing flames of oil or gas introduced thereto, is to reduce as much as possible of the sulfur dioxid contained in the gases entering said zone. While the ore is not materially changed in passing through this zone of the furnace, I- consider it advisable, inv most cases, to allow the ore to pass through this zone. However, withcertain kinds of ore, and under certain conditions, I may bypass the ore around or through this second zone, so that the ore will drop from the first zone (neutral or slightly reducing) to the third zone, hereinafter referred to. The ore is now conducted to a third section or zone of the furnace in which an oxidizing atmosphere is maintained, and a temperature high enough to oxidize the larger portion of, or as much as is desirable of, the sulfur remaining in the ore under treatment. From this third section of the furnace, the ore is discharged as usual into hoppers orcars for subsequent treatment, if desired. The

gases formed in this third section of the furnace and which contain S0 are conducted through the second section or zone of the furnace, in which the highly reducing, hot atmosphere is maintained, and are there largely reduced to elemental sulfur, which elemental sulfur then passes to and through the first section of the furnace, in which a non-oxidizing but preferably non-reducing, atmosphere is maintained.

By providing the three distinctly different sections described above, I prevent the elemental sulfur, either that distilled from the raw pyrites or that which is produced from S0 from coming into contact with any strongly reducing gases or particles of carorganic or carbonaceous compounds of Sn bon, and thus prevent the formation of any fur which might otherwise be formed.

The three-step'process above referred to.

is particularly applicable to the treatment of ores in which a large amount of pyrites exists. In the treatment of pyrrhotite or matte or similar material containing no considerable amount of feeble atom, the first zone above referred to could be omitted, and the ore subjected first to the strongly reducing atmosphere, and then to the 0Xl d1Z1I1g atmosphere, although it is found that the treatment of the ore, even when containing no considerable amount of feeble atom, first by the neutral flames, then by the h ghly reducing flames, and then by the oxidizing atmosphere gives excellent results.

The gases passing from the oxidizing zone contain considerable amounts of sulfur dioxid, which is reduced in the second or reducing zone. The gases leaving the reducing zone aid in maintaining the slightly reducing or neutral atmosphere in the first zone. The gases leaving the uppermost compartments of the furnace, or the neutral zone may be led off to any suitable device for the recovery of elemental sulfur therefrom.

While'I have described the process as being carried out in a multiple hearth furnace, I call attention to the fact that other types of furnaces could be used, c. g. a long single hearth furnace, pIOVlSlOIl being made for dividing it into zones for the carrying out of the successive steps. I now prefer, however, a multiple hearth furnace.

In my copending application, Serial No. 825,403, filed June 17, 1914, I have described and claimed a process of desulfurizing ores, such as pyrites, in which the ore,

preferably while being rabbled in the upper compartments of an ore roasting furnace of the multiple shelf type, is subjected to the action of a reducing or non-oxidizing flame,

and thereafter the ore is subjected to an oxidizing atmosphere, while at a temperature sufficiently high to convert the sulfur remaining in the ore into the form of sulfur dioxid. In the process of said application, the gases travel in the direction opposite to the travel of the ore.

In another copending application Serial No. 848,997, filed'July 3, 1914, I have described a process in which sulfid ore is first heated in a strongly reducing atmosphere, for example in the uppermost compartment or compartments of an ore roasting furnace, preferably of the multiple shelf type, after which the ore is subjected to the action of a substantially neutral (that is to say not strongly reducing and not oxidizing) flame and thereafter the ore is subjected, for example on the lower hearths of said furnace,

jecing' the ore to a temperature suflicient to distil a larger part of the-less stable atom of sulfur present in the raw ore, and in an atmosphere which is non-oxidizing; then passing the ore through another section of the same furnace, in which a highly reducing atmosphere is maintained, and a temperature preferably just under the fusin or .melting temperature 0 he materia under treatment; then pass'n the material through a third section of t e furnace, in which an oxidizing atmosphere is maintained, inwhich third section a greater or less amount of the sulfur remaining in the material under treatment is oxidized and sulfur dioxid, usually with some trioxid, present, and passing the gases and vapors formed throughout these successive steps in a direction opposite to that of the travel of the ore, thus providing means for the reduction of sulfur oxids formed in the third section of the furnace to be reduced to sulfur in their passage through the second section of the furnace, and also means for preventing either the oxidation or combination with carbonaceous matter of the elemental sulfur distilled in the first section of the furnace, as well as the elemental sulfur produced in the second section of the furnace.

metal sulfids which comprises subjecting said sulfids to the action. of a non-oxidizing flame, and thereafter subjecting saidsulfids, while in a heated state to oxidation, passing the gases produced in said step of oxidation into and through a space wherein said gases are subjected to a reducing atmosphere.

3. A process of separating sulfur from sulfid ore which comprises subjecting said ore to the action of a reducing flame, and thereafter subjecting said ore while in a heated state to oxidation, and drawing off the gases and vapors produced in eachof said steps, and mingling said gases and vapors together, within the space wherein the ore is subjected to the reducing flame, whereby the sulfur oxids produced in said oxidation are reduced, at'least in part, to elemental sulfur.

4. A process of separating sulfur from metal sulfids which comprises subjecting said sulfids to the action of a reducing flame, in a section of the furnace, and thereafter subjecting the same to an oxidizing.

2. A process of separating sulfur frompresent application is in part a con- 2 atmosphere in 'another section of the furnace, at a temperature at which a part at least of the sulfur will oxidize to S0,, passing the gases through the sections in which the successive steps are carried out in a direction opposite to the direction of travel of the sulfids through said compartments.

5. A process of separating sulfur from a sulfid ore which comprises subjecting said ore to a non-oxidizing flame in the absence of large amounts of steam, in which step the major portion of the feeble atom of sulfur is distilled, exposin said ore to a reducing flame after the feeble atom has been distilled, and in the absence of large amounts of steam, and then exposing said ore to an oxidizing flame and in the absence of material quantities of steam, said steps being successively performed upon a traveling stream of ore, passing the gases produced in the later steps, through the compartments in which the earlier steps are carried out, in contact with the reducing flame employed in said second step.

6. A process of Separating sulfur from sulfid ores, which comprises agitating said ores while treating the same with a nonoxidizing flame, thereafter subjecting said ores to oxidation, passing the gases produced in each of the stages of the process in a direction contrary to that of the ore under treatment, until said gases come into the influence of a reducing flame.

7. A process of separating sulfur from an ore containing both feeble atom of sulfur and fixed atom of sulfur, which comprises separating at least a portion of said feeble atom by subjecting said ore to a non-oxidizing flame, thereafter subjecting said ore to the action of oxidation, to convert a portion of the fixed atom of sulfur of said ore into an oxid of sulfur, subjecting said oxid of sulfur to the action of a reducing flame to reduce the same to elemental sulfur.

8. The method of operating a desulfurizing furnace, which consists of so controlling the atmosphere in the several parts of such furnace, that any oxid of sulfur formed in one part of the furnace where an oxidizing atmosphere is maintained, is subsequently reduced to elemental sulfur in another part of the same furnace, where a reducing atmosphere is maintained.

9. The method of operating a desulfurizing furnace which consists of distilling the major portion of the less stable atom of sulfur from a sulfid ore, in one portion of such furnace, by means of heat generated by incomplete combustion of any suitable hydrocarbon material, such incomplete combustion resulting in the production and maintenance of a hot non-oxidizing atmosphere in said portion of such furnace, thereafter causing the heated ore from which the major portion of the less stable atom of sulfur has been distilled and driven off, to travel to another portion of such furnace in which an atmosphere is maintained, rich enough in oxygen to oxidize the major portion of the sulfur remaining in said hot ore to oxids of sulfur, then causing these oxids of sulfur to travel to and through a portion of the furnace in which a hot reducing atmosphere is maintained, so that the said oxids of sulfur will be reduced to elemental sulfur in their passage through the hot reducing atmosphere.

10. A process of desulfurizing ores which comprises subjecting said ores, in a nonoxidizing atmosphere to a temperature at which at least the major portion of the less stable atom of sulfur is distilled from the ore in the form of elemental sulfur, passing the ore us treated to another part of the furnace an there subjecting the same to the influence 0 an oxidizing atmosphere, at a temperature at which at least a portion of the remaining sulfur is oxidized to 80,; passing the gases from the portion of the furnace in which the'SO is produced, into and through a part of the furnace in which a reducing atmosphere is maintained, in order to reduce at least the major portion of the S0 to elemental sulfur.

11. A process of desulfurizing ores which comprises subjecting said ores, to the action of a non-oxidizing atmosphere at a temperature at which the major portion of the less stable atom of sulfur is distilled from the ore in the form of elemental sulfur, passing the ore thus treated into another portion of the furnace and there subjecting the same to the influence of an oxidizing atmosphere at a temperature at which at least a portion of the remaining sulfur is oxidized to 80,; passing the gases from the portion of the furnace in which the S0 is produced into and. through a part of the furnace in which a strongly reducing atmosphere is maintained in order to reduce at least the major portion of the S0 to elemental sulfur.

12. A process of separating sulfur from a metal sulfid, which consists of so controlling the temperature and the reducing or oxidizing qualities of the atmosphere in different parts of the furnace in which the process is carried out, that the sulfid will first be subjected to a temperature of at least 700 C., in a non-oxidizing atmosphere, and later to a roasting temperature in an oxidia-- ing atmosphere, and passing the sulfurous gases from the oxidizing portion of the furnace through a portion of the furnace in which a high temperature and a strongly reducing atmosphere are maintained.

13. A process of separating sulfur from metallic sulfids which comprises first subjecting the ore in a non-oxidizing atmosphere, to a temperature at which the larger part of the less stable atom of sulfur distills in elemental form, then passing the 'ore around a second section of the furnace in which a highly reducing atmosphere is maintained, at a temperature high enough to reduce oxids of sulfur to the elemental form, then passing the material through a.

third zone of the furnace in which an oxidizing atmosphere is maintained and in which a part at least of the sulfur remainhot highly reducing atmosphere 15 

